Putting gas in your tank is fairly straight forward, complicated by the emission control "bellows" shroud over the nozzle. Trick is to retract it manually with the left hand, guiding it into the narrow hole. If you leave a little gap where you can look down into the filler hole slightly (wear your glasses as it can "spit back") and gas up at 1/2 to 1/4 speed...when you hear the gas rising near the nozzle it will bubble and should click the auto-shut off. If not, you can visually see when the gas is rising to the lower filler hole and DO NOT TOP OFF. Only if you are in a remote place where you are worried about running out, fill it right level to the low fill hole.
Yes, before I get a lot of grief...only do the top off thing if you are really worried about getting gas in remote areas, as the risk of spillage and overflow are high, unless you run out the extra gas for 25-50 miles. Know what your approximate fuel mileage is and rough calculate based on your tank size and what is perceived use.